A good site involves communication with visitors. Protect site! Also required are the protection of the site. It is desirable to provide comments and ask questions. Regardless of whether you will allow control of the publication will appear a lot of advertising content in the comments that have nothing to do with the published content.
How to get rid of unwanted comments?
Only install reCAPTCHA plugins.
CAPTCHA
CAPTCHA is a type of authentication used on websites to determine whether the user is human or program. The main goal is to prevent access to malicious programs. Once in a process (data entry, reporting, etc.). We want to check whether it is performed by a man or someone’s program (bot, crawler, spider or ant) activates the test to see is so designed that only a man can solve.
Common CAPTCHA tests require the user to enter several symbols (usually letters and / or numbers) which are shown in the picture, which is kind of distorted. Acronym CAPTCHA is an acronym that means fully automated Public Turing test to differentiate computers from humans (rus. Fully automated public Turing test to tell computers and humans apart.
Currently, the most perfect example is the following:
[Bvs_google_captcha]Excelent WordPress plugin is
More about it you can read Wikipedia.